Catalyst for synthesis of mercaptans



temperature.

3,214,386 QATALYM FOR SYNTHESIS OF MERCAPTANS Pant 1F. Warner andRichard D. Franz, Phillips, Tex.,

assignors to Phillips Petroleum Company, a corporation of Deiaware NoDrawing. @riginal application Oct. 20, 1961, Ser. No. 146,458, nowPatent No. 3,137,735, dated June 16, 1964. Divided and this applicationAug. 19, 1963, Ser. No. 303,153

(Ilaiins. (Cl. 252-429) This application is a divisional application ofapplication S.N. 146,458, filed October 20, 1961, now US. Patent3,137,735.

This invention relates to an improved process for preparing mercaptansby reacting an olefin with H 8 utilizing a novel catalyst, and to thenovel catalyst for the process.

The synthesis of mercaptans by reacting H S with an olefin is aconventional process. When utilizing relatively high molecular weightolefins, such as those containing from 9 to 16 carbon atoms permolecule, conducting the reaction at usual reaction temperatures withthe conventional catalyst, H PO -BF the yield of high molecular weightmercaptans is substantially reduced by fracturing of the olefins andproduction of a substantial proportion of lower molecular weightmercaptans. To illustrate, when reacting triisobutylene with H 8 toproduce tertiary dodecyl mercaptan, a substantial amount of butyl andoctyl mercaptans are produced. However, reduction of the temperature ofthe reaction below that at which fracturing of the heavy olefin isavoided results in low yield due to low activity of the catalyst, H PO-BF at low temperatures. This invention is concerned With a more activecatalyst for mercaptan synthesis at low temperatures.

Accordingly, it is an object of the invention to provide a process forpreparing mercaptans utilizing an improved catalyst. Another object isto produce mercaptans in improved yields at low temperatures. A furtherobject is to provide an improved catalyst for the synthesis ofmercaptans and by reacting H 8 and an olefin. It is also an object ofthe invention to provide an improved process for the synthesis ofmercaptans containing from 9 to 16 carbon atoms per molecule withimproved yield at low An additional object is to provide an improvedcatalyst containing the complex H PO -BF or H PO -BF which is moreeffective at low temperatures than this complex alone. Other objects ofthe invention will become apparent to one skilled in the art uponconsideration of the accompanying disclosure.

A broad aspect of the invention comprises a catalyst consistingessentially of a liquid complex of an oxygencontaining acid ofphosphorus, an alcohol of 1 to 5 carbon atoms, and B1 This catalyst isprepared by mixing the acid and the alcohol and adding B1 to themixture, preferably, to saturate the mixture wlth 'BF for highestactivity of the catalyst. The preferred acid is H PO but H3PO3 is alsoeffective. -(It is to be understood that where the ensuing disclosurerefers to H PO or phosphoric acid, H PO or phosphorus acid may be used.)The concentration of phosphoric acid is not critical and thecommercially available grade of 85% concentration is generally used.However, concentrations in the range of 40 to 100% are effective.

The alcohols useful in the catalyst are the C to C ited States Patent 03,214,386 Patented Oct. 26, 1965 alcohols including ethyl, methyl,propyl, butyl, and amyl alcohols. The ratio of alcohol to the acid inthe mix ture is in the range of 1:9 to 1:1 by Weight to be mosteffective. However, proportions outside of this range have someadvantage in the catalyst. The BF should be added to the liquid mixtureof acid and alcohol to the saturation point to provide the most activecatalyst, but lesser amounts produce a catalyst of proportionately lessactivity.

Another aspect of the invention comprises reacting H 8 with an olefinichydrocarbon in admixture with the H PO -BF alcohol complex to producethe corresponding mercaptan. This process produces high yield ofmercaptan, particularly, at temperatures in the range of 90 to 0 F. andpreferably in the range of 60 to 20 F. The process is conducted atpressures sutficient to maintain the reactants in liquid phase atreaction temperatures. Pressure depends upon the reactant mixture butpressures in the range of about 50 to 500 p.s.i.g. are generallysuitable. Conventional mol ratios of H 5 to olefin such as 1:1 to 6:1and preferably 2:1 to 5:1 may be used. The volume ratio of hydrocarbonfeed to catalyst is in the range of about 5:1 to 15: 1.

The olefinic hydrocarbons which may be reacted with hydrogen sulfide incarrying out this invention are those containing at least one ethylenicbond, and include aliphatic olefins, cyclic olefins, and substitutedaliphatic and cyclic olefins in which the substituting group or groupsmay be hydrocarbon or non-hydrocarbon radicals of such character thatthey do not interfere with the primary reaction. Typical olefins includeethylene, butylenes, cyclohexene, triisobutylene, and other C to Colefins.

Tertiary dodecyl mercaptan made from triisobutylene is particularlyuseful as a rubber modifier. Numerous synthesis runs have been madereacting triisobutylene with H S in admixture with H PO -BF catalyst andwith H PO -BF -CH OH. The following examples illustrate the use of theconventional catalyst H PO -BF and the catalyst of the invention inthese runs.

EXAMPLE I Triisobutylene was reacted with hydrogen sulfide in admixturewith boron trifiuoride-phosphoric acid catalyst made by saturatingphosphoric acid with boron trifluoride. The BF content of the catalystwas about 55 Weight percent. The feed stock was prepared by blending thetriisobutylene With hydrogen sulfide in a steel cylinder fitted with aneductor tube. The feed was metered with a Lapp pump through a pressurecontrolled relief valve into the reactor containing the catalyst. Theefiiuent passed through the phase separator and through another pressurecontrolled relief valve where the excess hydrogen sulfide flashed out.The crude mercaptan was collected in 1000 ml. cuts.

Synthesis conditions observed throughout the various four passoperations were as follows: hydrogen sulfide to olefin mole ratio ofabout 1.5; hydrocarbon to catalyst volume ratio in the reactor, about 9;feed rate of 1000-ml. of liquid efiiuent per hour; and pressure 350p.s.i.g. This pressure was chosen as being high enough to keep thereactants in liquid phase at all of the temperatures tested.

The liquid hydrocarbon eflluent was cut into three fractions, C and Cmercaptans (IBP to 340 F.), recycle TIB (340 to 400 E), and crude Cmercaptan (kettle product) in a Vigreux column. The crude C 3 mercaptanwas further purified by distillation in a 4-inch O.D. by 4-foot long,spinning band column. The unreacted olefin from the first pass wasrecycled with fresh H S to the second pass. The unreacted olefin fromthe second pass was recycled with H to the third pass, etc.,

A batch of catalyst was made using a mixture of methanol (75 ml.) and HPO (175 ml.) and this mixture was then saturated with BF The resultingcatalyst was then utilized in the synthesis of tertiary dodecylmercaptan from triisobutylene and H 5 under the same conditions asutilized in Example I at a temperature of -40 F. Comparison of the twocatalysts is made in Table II.

Table II Weight percent Catalyst Component BF3-II3PO4 BF3-H3PO4-CH3OHI-I3PO;(85%) 45 37 MethanoL 7 B F3 5G The yield per pass obtained withthe was 20 mol percent and the ultimate yield of tertiary dodecylmercaptan was 87 mol percent. This run demonstrates the more effectivecharacter of the catalyst of the invention at low temperatures, such as40 F., as compared with BF H PO catalyst.

The BF in the catalyst forms a complex with both the H PO and thealcohol and the alcohol renders the catalyst complex less viscous thanthe H PO 'BF complex.

Certain modifications of the invention will become apparent to thoseskilled in the art and the illustrative details disclosed are not to beconstrued as imposing unnecessary limitations on the invention.

We claim:

1. A catalyst consisting essentially of a liquid complex of an acid ofthe group consisting of H PO and H PO an alcohol of 1 to 5 carbon atoms,and BF said complex containing substantial and catalytically effectiveproportions of each named component.

2. A catalyst consisting essentially of a liquid mixture of a complex ofan acid of the group consisting of H PO and H PO with ER; and a complexof an alcohol of l to 5 carbon atoms and BF each said complex containingsubstantial and catalytically eifective proportions of its respectivecomponents.

3. The catalyst of claim 2 wherein said mixture is saturated with B1 4.The catalyst of claim 2 wherein said acid is I-I PO and said alcohol isCH OH.

5. The catalyst of claim 2 wherein the acid is H PO the alcohol is CHOH, the weight ratio of alcohol to acid is in the range of 1:9 to 1:1,and the mixture is saturated References Cited by the Examiner UNITEDSTATES PATENTS 2,469,335 5/49 Johnson et a1. 252433 2,515,123 7/50Hartough 252429 2,810,774 10/57 Serniuk 252433 2,889,370 6/59 Schechter252433 TOBIAS E. LEVOW, Primary Examiner.

SAM'UEL H. BLECH, Examiner.

1. A CATALYST CONSISTING ESSENTIALLY OF LIQUID COMPLEX OF AN ACID OF THEGROUP CONSISTING OF H3PO4 AND H3PO3, AN ALCOHOL OF 1 TO 5 CARBON ATOMS,AND BF3, SAID COMPLEX CONTAINING SUBSTANTIAL AND CATALYTICALLY EFFECTIVEPROPORTIONS OF EACH NAMED COMPONENT.